Marcos,
I also have a beagle the exact same age with VERY BAD allergies. I am interested to know what state you are in to see if it is from the same breeder.
My breeder is also saying there are no more that have the problem in the litter but I know that allergies of this kind can be passed on through parents and others may also have this problem. We have been seeing a dermatoligist for our bagle and have her on Atopica and injections to try and get her over it. I know it is not a nice thing to see a new puppy with such awful scratching. Unfortunately I had to have our beautiful girl steralised so she can not breed because we just could not let this happen to any other puppies.